Hooke's law and force-extension graphs Quiz
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5 questions, one answer each
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1. A spring has a stiffness of 25 N m⁻¹. What force extends it by 0.30 m, within its limit of proportionality?
- A. 0.012 N
- B. 7.5 N
- C. 83 N
- D. 75 N
2. On a force-extension graph with force on the vertical axis, what does the gradient of the straight section give?
- A. The energy stored
- B. The extension at the elastic limit
- C. The stiffness k
- D. The yield point
3. A wire is stretched beyond its elastic limit and then unloaded. What is observed?
- A. It returns exactly to its original length
- B. It is left with a permanent extension
- C. It becomes shorter than its original length
- D. Its stiffness increases to infinity
4. Which statement describes the yield point of a ductile metal?
- A. The wire snaps
- B. Hooke's law is first obeyed
- C. The wire stretches a large amount for little or no increase in force
- D. The wire returns to its original length
5. A spring obeys Hooke's law up to 10 N. A force of 15 N gives an extension greater than predicted by F = kx. Which is the best explanation?
- A. 15 N is beyond the limit of proportionality
- B. The stiffness of the spring has increased
- C. The spring was compressed
- D. The spring has not yet reached its elastic limit, so Hooke's law applies exactly